Telephony.



No. 756,436. PATENTED APR. 5, 1904.

J. TROWBRIDGE. I

TELEPHONY.

APPLICATION FILED MAY 1a, 1903.

N0 MODEL. 2 SHEETBSHEET 1.

M65595" I I Jul/em): I

'. PATBNTED APR. 5-1904.

J. TROWBRIDGE.

' TELEPHONY-- APPLICATION FILED MAY 18, 1903.

2 SHEETS- 81E331 2- N0, MODEL.

JWIKJSZ UNITED STATES iatented April 5, 1904.

P TENT OFFICE.

TELEPHONY.

SPECIFICATION forming part of Letters Patent No. 756,436, dated April 5,1904.

Application filed May 18, 1903. Serial No. 157,560. No model.)

To all whom, it may concern.-

Be it known that I, J OHN TROW'BRIDGE, a citizen of the United States, and a resident of Cambridge, in the county of Middlesex and State of Massachusetts, have invented new and useful Improvements in Telephony, of which. the following is a specification.

The object of my invention is to relay or repeat telephonic current undulations in such manner that relatively feeble undulations in one telephone-line will be reproduced in another line with enhanced force and amplitude and without impairment of the essential telephonic character of the current undulations and consequent deterioration of articulation and to provide such a relay apparatus that the telephonic system as a whole, including relays,will reciprocatethat is tosay, will transmit speech messages electrically in either direction, as in the case of the ordinary continuous line.

My invention also includes means for amplifying and strengthening the speech-producing articulate undulations as they are being transformed into mechanical vibrations and sound-wavesin short, involves the construc tion and mode of operation of an improved telephone-receiver.

In United States Letters Patent to Samuel Sheldon and myself, No. 407,799, dated July 30, 1899, there is described a device whereof the purpose was to utilize powerful 'electro dynamic currents to energize magnets in a relay apparatus. This apparatus was also intended for use as a receiving instrument. As the continuous current generated by adynamo involves the employment of a commutator, there is set up in the current a rapidly-recurring series of pulsations or throbs, due to the action of the commutator, and as was pointed out in the said Patent No. 407,799 the inductive pulsations producedbythe commutator wherever an armature-coil is employed which intersects the lines of force of the surrounding magnetic field (such as illustrated by Siemenss patent, No. 149,797, dated April 14, 1874) will if the armature be employed as part of a telephonic system overpower the more delicate undulations characteristic of a telephonic current. Consequently, as the specification of the Trowbridge and Sheldon patent, No. 407,799, sets forth in detail, the object was to arrange an armature wound and suspended in the field of a dynamo-currenteXcited electromagnet in such a manner as to elude the disturbing commutator influences, and thus be capable of transmitting speech as a relay or as a receiver. Unfortunately for the practical accomplishment of this purpose the hypothesis of the said PatentNo. 407,799 failed to take account of other factors, both electromagnetic and mechanical, and consequently the apparatus as a whole, although it obviated the difliculties due to commutator disturbances, failed satisfactorily to transmit the electrical undulations characteristic of and essential to the production of articulate speech sounds. The net failure of the said apparatus may be correctly characterized thus: The instrument of Patent No. 407,799 whether used as a relay or as a receiver was incapable of transmitting through its several transforming members unimpaired and constant in character thetelephonic undulations of the incoming line. The undulations emitted by the instrument were more or less confused with disturbing undulations superposed upon the correctly-modulated incoming waves or pulsations, so that when finally transformed into sound-waves they lost in whole or in part the essential quality of articulate speech. This imperfection was usually manifested by confused buzzing or rattling sounds, which always interfered with and often destroyed the pure essential articulate speech sounds. The Patent No. 407,799, however, set forth a mode of enhancing or amplifying the feeble undulations of a nearly-exhausted telephonic current by converting the undulations thereof into magnetic undulations Within a supplemental magnetic field, although, as I have pointed out and as experience proved, the mode of accomplishing this result shown in the said I patent failed to take account of many then unsuspected conditions, and thus failed to produce the useful result of transmitting and forwarding with unimpared articulation the 'un dulations of the incoming current.

'I have discovered the electrical and mechanical causes of the defects of the instruments described in Patent No. L07 ,7 99 and have by my present invention herein set forth provided an apparatus which by the aid of asupplemental magnetic field amplifies the feeble undulations of a nearly-exhausted telephone-line and repeats or transmits them unimpaired in articulate quality to a second line, thus preserving the exact undulatory correspondence with the sound-waves of articulate speech. My invention consists of a novel method of repeating electrical undulations and also of an apparatus which employs my new method to transmit and repeat telephonic messages. In an application for United States Letters Patent, Serial No. 157, 561,filed concurrently herewith, I have shown and claimed my said apparatus, and I therefore wish it to be understood that while this specification for purposes of explanation involves a description of my apparatus I re serve the same in whole and part for claim in the said concurrent application.

In the drawings hereto annexed, Figure 1 is a plan view, partly diagrammatic and conventional, of a telephonic repeating instrument or relay embodying my invention. Fig. 2 is a diagram of a complete telephone-line with asingle reciprocating relay-station. Fig. 3 is a diagramof a non-reciprocating telephone-line with two relays arranged tandem. Fig. 4 is a diagram of a reciprocating tandem relay-line, and Figs. 5 and 6 show other forms of relays or repeating instruments.

Referring to Fig. 1, upon a suitable base and by means of brackets M M are mounted a pair of horseshoe-magnets M M. These may be permanent magnets or electromagnets. In the latter case they should be energized by a continuous and steady current, as from a primary or storage battery. Likewise mounted on the base is a telephonic transmitter T, which is here shown asa solid-back carbonbutton transmitter. Firmly and rigidly mounted on the impulse-receiving member of the transmitter T, as by a stem P, there is an armature A, which is preferably composed of soft-iron rods or short Wires. At the ends of the armature A are secured transverse polepieces a a, likewise of soft iron. I have found by experiment that these pole-pieces while not essential to the performance of my new method nevertheless increase the responsive delicacy of the instrument. The magnets M M are arranged with their north and south poles N S mutually opposite each other, or, in other words, the north poles of the magnetsM M are diagonally opposite, as also are the south poles. The resulting induced polarity of the armature pole-pieces a a is as shown in Fig. 1 by the letters a 8. Adjusting-screws M enable the operator to adjust the magnet-poles N S as close as desired to the armature pole-pieces. These screws should be of brass or other diamagnetic material.

The magnets M M should be of equal strength, so as to maintain substantial equilibrium in the field and with respect to the armature A.

The mode of mounting the magnets M M in polar opposition, as shown, establishes a field which may be described as quadrilateral and symmetrical or balanced, and the armatureA is normally in a state of equilibrium, the balanced forces of the magnetic field exerting no stress upon the impulse-receiving member of the transmitter T. This condition I regard as important, because the transmitter T, whatever be its specific character, is thus maintained in precisely the same delicately-responsive state that characterizes a transmitter which is prepared in the usual and proper way for the reception of sound-waves. I have found by careful experiment that with an armature in an unbalanced magnetic field connected directly to a transmitter-say to a diaphragmthe constant pull of the magnetic field causes a distortion of the impulse-receiving member of the diaphragm, and consequently produces disturbing effects, which obscure the proper articulation of the instrument.

The incoming telephonic line L we will suppose to be at such a distance from the transmitting devices at its remote end that the electrical undulations are feeble, so that reproduction of audible speech thereby in the usual manner is impracticable. In circuit with the line L, I wind an armature-coil Z on the armature A, preferably bunching the coil in two parts near the ends of the armature, leaving the middle portion thereof bare of coil, and thus obtaining practically all the electromagnetic efiect of the coils Z, While saving weight.

The transmitter T is wired in the usual manner, having a battery B of proper strength in its immediate circuit. In this circuit is also located the primary of an induction-coil I, whereof the secondary is in the outgoing or relay line B.

When the incoming line L is quiet and no electrical undulations are passing on it, the relay instrument is in equilibrium; but when electrical undulations are set up in this line the polarity of the armature A is varied in exact correspondence and consonance with the electrical undulations in the line L,and an undulating or vibrating magnetic field is generated in the supplemental field of themagnets M. The resulting effect is the product of the armaturecoil effects and the supplemental field effects, and the magnetic, and consequently the mechanical, results are enhanced and amplified. Within quite generous limits the strength of the supplemental magnetic field may be raised and the consequent product effects increased. Moreover, by means of the polar relationship of the field and armature coil all torsional moments are in equilibrium, and the resultant mechanical vibrations are in a straight line and are exerted in this straight line perpen- IIO the induction-coil 1 in circuit.

dicularly to the impulse-receiving member of the transmitter T and perpendicularly to the planes of contact between the resistance-varying members of the transmitter. This same rectilinear transmission of mechanical effects and perpendicular impact may readily be secured, whatever be the structural character of the transmitter. By preserving these conditions the relay or repeating instrument sends to the outgoing or relay line B undulations precisely corresponding to the incoming undulations of the line L, which excite the armature-coil Z and bring into action the vibration-amplifying forces of the supplemental field of the magnets M. Thus the transmitter T is impressed with undulating impulses which are essentially the same in articulate character as the sound-waves which excited the sending instrument at the remoteend of the line L, and consequently transmits to the line B unimpaired in articulate quality undulations essential to the production of intelli gible articulate speech, which may then be made manifest by a proper telephonic receiver at the remote-end of the line H.

The relay or amplifying effect sensible at the receiver end of the line B is due to several conditions: first, the product magnetic amplifications of the armature-coil undulations by means of the supplemental magnetic field, whereby the mechanical impressupon the transmitter T is emphasized; second, to the relay battery B, which supplies fresh electrical energy for transmission of undulations along the line R, and, third, to the preservation and transmission unimpaired and unobscured by extraneous influences of the articulation of the original telephonic current.

In Fig. 2 there is illustrated by diagram an.

arrangement for obtaining reciprocal relay effects between two distant stations. At one station is located the usual transmitter T,

with battery B and the primary of the induction-coil I in its circuit. The line L, including the secondary of the induction-coil 1, armature-coil at A, the secondary of the induction-coil 2', and the receiver R, leads to the,

relay-station. At this relay-station two instruments similar, to that shown in Fig. 1 and above described are set up, the instrument M M A T in adjustment to receive and repeat impulses from transmitter T and the instrument m m a t" to receive and repeat impulses from transmitter T, which is at the end of the line remote from the transmitter T. The two relay instruments at the relay-station are arranged as follows: The same circuit R.in-.

cludes' the two transmitters T. and t, the relaybattery B, and the primaries of inductioncoils I and a. .At the station remote from the instrument T and R is located the transmitter T with the battery 13 and the primary of The line L includes the secondary of induction-coil 1 the receiver R armature a, and the secondary of Fig. 1, these magnetic undulations are reconverted into electrical undulations precisely corresponding'to the original speech vibrations at the transmitter T, and these undula tions in circuit R set up corresponding undulations in the circuit L which are in the usual manner finally reconverted into sound-waves at the receiver R where the speech delivered at the transmitter T is reproduced.

The current undulations of the circuit L passing through the secondary of the coil produce in its primary no sensible elfect. Thus the resistance to the transmission of undulatory effects backward, as we 'may say, through the relay instrument m m a t is practically prohibitory.

W hen speech is made at transmitter T the reciprocal effect is perfect. The'relay m m a 25 receives, amplifies, and transmits the undulations to the line L through the inductioncoil 2', and the receiver R. reconverts them into speech. Whatever be the source of undulations, the effective relay instrument takes the message and repeats it. One relay works in one direction, the other in the opposite direction, and each automatically to the exclusion of the other. The practical results, therefore, which appeal to the users of the instruments at the ends of the line are the same as if they were conversing over a simple telephone-line short enough to render the direct communicating .undulatory current eifective.

The preservation of the exact' articulate character of the undulatory current, which is peculiar to my method ofrepeating, enables one to use several relays like that shown in Fig. 1 or relay-stations like that shown in Fig. 2 in tandem. I illustrate a simple non-reciprocatingtandem relay-line in Fig. 3. Therein the impulses from transmitter T excite the relay at station 1. Thence the undulatory current is passed on amplified to station 2 and thence to receiver R In Fig. 4: I illustrate an arrangement of complete reciprocating relay-stations-in tandem. In this system the arrangement of terminal station T R with relation to relay-station 1 and that of terminal station T R with relation to relay-station 2 is the same as the relations of the respective terminal stations of Fig. 2 to the relay system. The secondary of the induction-coil I, the armature-coil of relay instrument 2*, the secondary of induction-coil i and the armature-coil of relay instrument 1 are in the line which stretches between rerectilinear mechanical movements.

ciprocally as readily as an ordinary short telephone-line.

It will be observed that in contrast with the instrument and mode of operation described in Patent No. 407 ,7 99 I have by my present invention produced the following electrical, magnetic, and mechanical conditions: Instead of converting the product effects of an armature and surrounding field into rotary movements by means of unbalanced torsional magnetic product effects characteristic of the said patent I have maintained torsional balance in magnetic efiects and produced direct Whereas in the instrument of Patent No. 407,7 99 the curvilinear mechanical impulses of the suspended armature caused distortions and disturbances in the transmitter, in my present invention no such distortion or disturbance takes place. Instead of making contact between the armature-coil and the receiving members of a transmitter by means of initial pressure (itself a cause of mechanical distortion and confusion of articulate with inarticulate electrical undulations) I have secured the armature-coil directly and rigidly to the receiving member of the transmitter, thus avoiding any confusing stresses and also eliminating the efi ect of individual non-electric vibrations of the independently-suspended armature. In short, I have by my present invention contrived a method and apparatus whereby a symmetrical or balanced magnetic field as an independent source of power is enabled, in coaction with an exciting-armature, to repeat unimpaired thearticulate undulations of a telephonic circuit with fresh and amplified transmission-impulses in a second or relay circuit, whereas by the apparatus and mode of operation shown in Patent No. 4=07,79 9 this functional result could not be obtained; also I have by my present invention contrived a method and apparatus whereby the symmetrical or balanced magnetic field, in connection with an exciting-armature, may be employed to directly produce the mechanical vibrations at one end to the middle of the metallic dia phragm and at its opposite end to the middle of the usual mica diaphragm closing the end of the electrode-holder and against which the fix the two magnets M within the casing of the transmitter, properly disposed with relation to the iron armature A.

In Fig. 6 I have shown another form of instrument, which difiers from that above described in that a block D of white wood is fixed to the middle of the metal diaphragm, and in this block D the armature A is mounted with only its two ends projecting therefrom. I By thus practically burying the armature in the block of wood D independent conflicting vibrations of said armature are prevented, the inclosing body of wood tending to smother the same without itself being vibrated.

In telephone systems comprising a plurality of repeating instruments I find that it is desirable to make each adjustable-that is, to

provide some means by which the action ofeach instrument may be regulated or tuned, so as to work in harmony with the other instruments of the system. To this end I may provide each instrument with a spring-finger d, fixed to any suitable support and arranged to press through a block of rubber 61 upon the side of the block D. The pressure of the spring-finger d may be regulated by means of a screw d, by means of which the action of the instrument may be regulated to accord with the other instruments of the system. The arrangement shown in Fig. 5 has the advantage of supporting the vibrating armature A at both sides, so that the slight bending effect due to the weight of the armature is wholly obviated. Any support at the side away from the transmitter T will serve for this purpose;

but I prefer to employ a diaphragm clamped at its periphery for two reasons: First, the diaphragm does not tend to confuse the pure articulate vibrations of the armature by inderelay instruments are so slight as to be negligible; but with a tandem arrangement employing several relay-stations the local disturbances negligible with a single station are liable to accumulate at each relay and should be suppressed.

' What I claim is- 1. The method of transmitting messages which consists in transforming electrical undulations into qualitatively corresponding magnetic undulations within a supplemental magnetic field, producing thereby qualita tively corresponding resultant magnetic product undulations, and causing qualitatively corresponding mechanical vibrations quantitatively proportionate to the resultant magnetic product undulations, thereby quantitatively enhancing the mechanical result while preserving therein the characteristic quality of the original electrical undulations.

2. The method of transmitting messages which consists in transforming electrical undulations into qualitatively corresponding magnetic undulations within a supplemental magnetic field, producing thereby qualitatively corresponding resultant magnetic product undulations, establishing. and maintaining a symmetrical relation between the forces of the supplemental field and the electrically-induced magnetism respectively, and transforming the resultant magnetic product undulations into qualitatively corresponding mechanical vibrations.

3. The method of transmitting messages which consists in transforming electrical undulations into qualitatively corresponding magnetic undulations within a supplemental magnetic field, producing thereby qualitatively corresponding resultant magnetic product undulations, equilibrating the torsional effects of the resultant magnetic product undulations and causing thereby qualitatively corresponding mechanical vibrations quantitatively proportionate to the resultant magnetic product undulations, thereby quantitatively enhancing the mechanical result while preserving therein the characteristic quality of ,the original electrical undulations.

4. The method of transmitting messages which consists in transforming electrical undulations into qualitatively corresponding magnetic undulations within a supplemental magnetic field, producing thereby qualitatively corresponding resultant magnetic product undulations and producing by means of the said product undulations rectilinear mechanical vibrations quantitatively proportionate tothe resultant magnetic products and qualitatively corresponding to the original electrical undulations.

5. The method of transmitting messages which consists in transforming electrical undulations into qualitatively corresponding magnetic undulations within a supplemental magnetic field, producing thereby qualitatively corresponding resultantmagnetic product undulations, and causing qualitatively corresponding mechanical vibrations quantitatively proportionate to the resultant magnetic product undulations, thereby quantitatively enhancing the mechanical result while preserving therein the characteristic quality of the original electrical undulations, and causing qualitatively corresponding electrical undulations by means of said mechanical vibrations.

6. The method of transmitting messages which consists in transforming electrical undulations into qualitatively corresponding magnetic undulations within a supplemental magnetic field, producing thereby qualitatively corresponding resultant magnetic product undulations, equilibrating the torsional effects of the resultant magnetic product undulations and causing thereby qualitatively corresponding mechanical vibrations quantitatively proportionate to the resultant magnetic product undulations, thereby quantitatively enhancing the mechanical result while preserving therein the characteristic quality of the original electrical undulations, and causing qualitatively corresponding electrical undulations by means of said mechanical vibrations.

7. The method of transmitting telephonic messages which consists in transforming electrical undulations into qualitatively corresponding magnetic undulations within a supplemental magnetic. field, and producing by means of the said resultant magnetic product undulations rectilinear mechanical vibrations, quantitativelyproportionate and qualitatively corresponding to the resultant magnetic product undulations and causing qualitatively corresponding electrical undulations therewith.

8. The method of transmitting telephonic messages, which consists in transforming electrical undulations into qualitatively corresponding magnetic undulations in a normally symmetrically balanced supplemental magnetic field, andthereby causing magnetic undulatory product effects, equilibrating the torsional tendencies of the magnetic product undulations or disturbances, and transforming the resultant of the said magnetic product undulations into qualitatively correspondingmechanical vibrations.

9. The method of transmitting telephonic messages, which consists in transforming electrical undulations into qualitatively corresponding magnetic undulations in a normally symmetrically balanced supplemental magnetic field, and thereby causing magnetic undulatory product efiects, equilibrating the torsional tendencies of the magnetic product undulations or disturbances, and transforming the resultant of the said magnetic product undulations into qualitatively corresponding rectilinear mechanical vibrations.

10. The method of transmitting messages which consists in transforming electrical undulations into qualitatively corresponding magnetic undulations within a supplemental substantially constant magnetic field, producing thereby qualitatively corresponding resultant magnetic product undulations, and causing qualitatively corresponding mechanical vibrations quantitatively proportionate to the resultant magnetic product undulations, thereby quantitatively enhancing the mechanical result While preserving therein the characteristic quality of the original electrical undulations. g

11. The method of transmitting messages Which consists in transforming electrical undulations into qualitatively corresponding magnetic undulations Within a substantially constant supplemental magnetic field, producing thereby qualitatively corresponding resultant magnetic product undulations, establishing and maintaining a symmetrical, relation between the forces of the supplemental field and the electrically-induced magnetism respectively and transforming the resultant magnetic product undulations into qualitatively corresponding mechanical vibrations.

12. The method of transmitting messages Which consists in transforming electrical undulations into qualitatively corresponding magnetic undulations Within a substantially constant supplemental magnetic field, producing thereby qualitatively corresponding resultant magnetic product undulations, equilibrating the torsional effects of the resultant magnetic product undulations and causing thereby qualitatively corresponding mechan ical vibrations quantitatively proportionate to the resultant magnetic product undulations, thereby quantitatively enhancing the mechanical result While preserving therein the characteristic quality of the original electrical undulations.

13. The method of transmitting messages Which consists in transforming electrical undulations into qualitatively corresponding magnetic undulations Within a substantially constant supplemental magnetic field, producing thereby qualitatively corresponding resultant magnetic product undulations and producing by means of the said product undulations rectilinear mechanical vibrations quantitatively proportionate to the resultant magnetic products and qualitatively correspond ing to the original electrical undulations.

14:. The method of transmitting messages which consists in transforming electrical undulations into qualitatively corresponding magnetic undulations Within a substantially constant supplemental magnetic field, producing thereby qualitatively corresponding resultant magnetic product undulations, and causing qualitatively corresponding mechanical vibrations quantitatively proportionate to the resultant magnetic product undulations, thereby quantitatively enhancing the mechanical result While preserving therein the characteristic quality of the original electrical undulations, and causing qualitatively corresponding electrical undulations by meansofi" said mechanical vibrations. W

15. The method of transmitting messages Which consists in transforming electrical undulations into qualitatively corresponding, magnetic undulations Within a supplemental substantially constant magnetic field, producing thereby qualitatively corresponding resultant magnetic product undulations, equilibrating the torsional efiects of the resultant magnetic product undulations and causing thereby qualitatively corresponding mechanical vibrations quantitativ ely proportionate to the resultant magnetic product undulations, thereby quantitatively enhancing the mechanical result While preserving therein thechar acteristic quality of the original electrical un. dulations, and causing qualitatively corresponding electrical undulations by means of said mechanical vibrations.

16. The method of transmitting telephonic messages which consists in transforming electrical undulations into qualitatively corre-. sponding magnetic undulations Within a supplemental substantially constant magnetic field, and producing by means of the said resultant magnetic product undulations rectilinear mechanical vibrations quantitatively v proportionate and qualitatively corresponding to the resultant magnetic product undulations, and causing qualitatively corresponding electrical undulations therewith. I

' 17 The method of transmitting telephonic messages, Which consists in transforming electrical undulations into qualitatively corresponding magnetic undulations in a normally symmetrically balanced substantially constant supplemental magnetic field, and causing magsponding magnetic undulations in a normally I,

symmetrically balancedsubstantiallyconstant supplemental magnetic field, and causing magnetic undulatory product effects, equilibrating the torsional tendencies of the magnetic product undulations or disturbances, and transforming the resultant of the said magnetic.

product undulations into qualitatively corresponding rectilinear mechanical vibrations.

Signed by me at Boston, Suffolk county, Massachusetts, this 12th day of May, 1903.

JOHN TROWBRIDGE.

Witnesses:

ODIN ROBERTS, ARTHUR F. RANDALL.

netic undulatory product effects, equilibrating I transmitting telephonic 

